Question: All of the 4th grade teachers and students from Santa Rita went on a field trip to an archaeology museum. Tickets were $$8.00$ each for teachers and $$2.50$ each for students, and the group paid $$39.00$ in total. A few weeks later, the same group visited a science museum where the tickets cost $$32.00$ each for teachers and $$8.50$ each for students, and the group paid $$147.00$ in total. Find the number of teachers and students on the field trips.
Answer: Let $x$ equal the number of teachers and $y$ equal the number of students. The system of equations is: ${8x+2.5y = 39}$ ${32x+8.5y = 147}$ Solve for $x$ and $y$ using elimination. Multiply the top equation by $-4$ ${-32x-10y = -156}$ ${32x+8.5y = 147}$ Add the top and bottom equations together. $ -1.5y = -9 $ $ y = \dfrac{-9}{-1.5}$ ${y = 6}$ Now that you know ${y = 6}$ , plug it back into $ {8x+2.5y = 39}$ to find $x$ ${8x + 2.5}{(6)}{= 39}$ $8x+15 = 39$ $8x = 24$ $x = \dfrac{24}{8}$ ${x = 3}$ You can also plug ${y = 6}$ into $ {32x+8.5y = 147}$ and get the same answer for $x$ ${32x + 8.5}{(6)}{= 147}$ ${x = 3}$ There were $3$ teachers and $6$ students on the field trips.